The present invention relates to a method for forming a prosthetic mesh having one or more barbed suture(s) attached thereto, such a prosthetic mesh being useful in the surgical field. The method of the invention allows producing a prosthetic mesh having one or more barbed suture(s) attached thereto in a reduced time and in a very cost-effective way.
The abdominal wall in humans is composed of fat and muscles interconnected by fascias. It sometimes happens that a break in continuity occurs in the fascias, allowing part of the peritoneum to slip through and form a sac, or a hernia, containing either fat or part of the intestines. Hernias or incisional hernias (a hernia occurring through a parietal surgical scar) show themselves in the form of a bulge at the surface of the skin and are classed, for example, as umbilical or inguinal hernias or incisional hernias, depending on where they are located.
In order to repair a hernia defect, surgeons often fit a prosthesis in place which is made of synthetic mesh and replaces or strengthens the weakened anatomical tissues.
Within the meaning of the present application, a “mesh” is understood as an arrangement of biocompatible yarns, such as a textile or fabric, preferably open-worked, that is to say provided with pores that favour recolonization of tissue such as cellular growth. Such a mesh can be bioresorbable, permanent or partially bioresorbable. It is sufficiently flexible to be folded up at the time of introduction into the abdominal cavity.
Meshes for forming hernia prosthesis are well known to a person skilled in the art. The mesh can be supplied in any shape whatsoever, for example rectangular, square, circular, oval, etc., and can then be cut to suit the shape of the hernia defect. For example, the overall shape of the mesh can be circular or oval. Alternatively, the mesh can have a generally square shape or a rectangular shape.
Meshes for forming hernia prosthesis are advantageously provided as a knitted structure obtained with biocompatible yarns. Knitting methods allow obtaining knitted structure having openworked faces that promote cell recolonization after implantation.
Once implanted, the mesh must be fixed to the surroundings biological tissues, such as for example the abdominal wall. Many fixing means are available for fixing the mesh to the abdominal wall, such as tacks, staples, adhesives or sutures.
The use of sutures usually imply forming surgical knots in order to anchor the suture.
Surgical knots have been used for ages in order to anchor and allow a conventional suture, in other words a smooth suture without barbs, to perform its role in mesh fixation for example. Anyway, surgical knots reduce the tensile strength of conventional sutures by thinning and stretching the material forming the suture. Indeed, it is known that the weakest portion of any suture line is the knot.
Moreover, the tying of surgical knots introduces the potential of human error. A knot-secured conventional suture may create an uneven distribution of tension across the wound, with the higher tension burden placed at the knots. In addition, in minimally invasive laparoscopic surgery, the ability to quickly and properly tie surgical knots presents a challenge. The skill necessary for performing intra- or extracorporeal knot tying for laparoscopic surgery may be acquired only with practice and patience, yet surgeons need to master such a skill in order to properly perform closure procedures. Laparoscopic knot tying is also more mentally and physically stressful on surgeons.
Given the excessive relative wound tension on the knot and the reasonable concerns of surgeons for suture failure due to knot slippage, there is a natural tendency toward overcoming these potential issues by over-tightening knots. However, tighter knots may be worse for wound healing and strength than looser knots. Surgical knots, when tied too tightly, can cause localized hypoxia, reduced fibroblast proliferation, and excessive tissue overlap, leading to reduced strength in the healed wound.
Eventually, a surgical knot yields the highest density of foreign body material in any given suture line and the volume of a knot may be directly related to the total amount of surrounding inflammatory reaction. If minimizing the inflammatory reaction in a wound is important for optimized wound healing, then minimizing knots sizes or even eliminating knots altogether would be beneficial as long as the wound-holding strength of the suture line is not compromised.
For all these reasons, the use of barbed suture, suture with barbs, has tremendously increased in the past years. In particular, one of the most costly parts of a surgical procedure is time in the operating room.
Barbed sutures are known. They basically consist in strands of smooth suture provided with barbs on their surfaces. Barbed sutures are generally made of the same materials as conventional sutures and offer several advantages for fixing meshes to the abdominal wall compared with conventional sutures. A barbed suture includes an elongated body that has one or more spaced barbs, that project from the surface of the suture body along the body length.
The barbs are generally arranged to allow passage of the barbed suture in one direction through tissue but resist movement of the barbed suture in the opposite direction (one-way suture). One advantage of barbed sutures is the provision of a non-slip property.
Barbed sutures are known for use in laparoscopic and endoscopic procedures. The number of barbs needed for a particular suture may be influenced by the size of the wound and the strength required to fix the mesh. Like a conventional suture, a barbed suture may be inserted into tissue using a surgical needle.
In some circumstances, a random configuration of barbs on the exterior surface of the suture is preferred to achieve optimal fixing of the mesh. However, in other circumstances, where the tissue repair needed is relatively small, a reduced number of barbs may be desired.
Various methods of forming barbs on sutures have been proposed such as mechanical cutting, laser cutting, injection molding, stamping, extrusion and the like. However, such methods may be difficult or costly, in particular when a specific arrangement or configuration of barbs is needed for an appropriate surgical procedure.
For example, conventional cutting methods of forming barbs may involve cutting with a blade into the elongate body of the suture, where the elongate body may be a monofilament for example. Barbed sutures may be fabricated from monofilament fibers by a micro-machining technique, which escarpes barbs into the fiber around the circumference in a variety of configurations. Cutting meth s have therefore significant drawbacks as they weaken the core of the suture and narrow its functional diameter. Moreover, they are costly and have slow manufacturing cycle time.
Accordingly, there is a continuous need for methods of forming barbs on a suture that are less difficult to implement, more efficient and cost effective. There is also a continuous need for methods allowing varying the size, the location and the depth of the barbs, as well as the amount of barbs present on the suture, depending on the contemplated surgical application.
In particular, there is a need for providing a mesh having one or more barbed suture(s) attached thereto, so that the surgeon does not have to waste time looking for a suture at the time he needs to fix the mesh to the biological tissue during the implantation.
A first aspect of the invention is a method for forming a prosthetic mesh having at least a barbed suture attached thereto, said barbed suture comprising an elongate body provided with barbs extending substantially radially out from said elongate body, said method comprising the following steps:
a) producing a knitted structure on a warp knitting machine comprising at least one needle-bed comprising at least three guide bars, a first guide bar B1, a second guide bar B2 and a third guide bar B3, said first guide bar B1 being threaded with first yarns of a biocompatible material, said second guide bar B2 being threaded with second yarns of a biocompatible material, said third guide bar B3 being threaded with third yarns of a biocompatible material, said knitted structure being produced on a determined length along the warp direction corresponding to a total number of N stitches ranging from 1 to N completed along said warp direction by the machine, N being an integer above 7, wherein                i) a first knit portion is produced along stitches ranging from 1 to x, where 1<x<N, in which the knitting patterns followed by the first, the second and the third guide bars (B1, B2, B3) produce an openworked knit capable of favoring cellular growth,        ii) a second knit portion is produced for stitches ranging from (x+1) to N, in which the knitting pattern followed by said second and third guide bars (B2, B3) produces chain stitches and the knitting pattern followed by the first guide bar B1 produces at least a partial weft in which said first yarns complete weft stitches with at least one of said chain stitches, thereby producing at least one weft stitched chain stitch,        
b) cutting the second knit portion along the warp direction on both sides of said at least one weft stitched chain stitch and along an edge separating the second knit portion from the first knit portion, so as to remove the second knit portion from the knitted structure while maintaining said weft stitched chain stitch attached to the first knit portion,
wherein the first knit portion forms the mesh and the second or third yarn forming part of said at least one weft stitched chain stitch forms said elongate body of said barbed suture attached thereto, the first yarns cuts extending from said weft stitches of said at least one weft stitched chain stitch forming said barbs of said barbed suture.
In the prosthetic mesh obtained by the method of the invention, the barbed suture therefore comprises an elongate body made of a yarn of a biocompatible material coming either from guide bar B2 (second yarn) or from guide bar B3 (third yarn), provided with barbs extending substantially radially out from said elongate body, said barbs being first yarns cuts made of a biocompatible material, where said first yarns cuts are stitched to said second or third yarn forming said elongate body. The first yarn cuts result from the cutting of the second knit portion on both sides of the at least one weft stitched chain stitch. In embodiments, said elongate body(ies) of said barbed suture(s) is/are formed of second yarns only.
In the present application, “N” and “x” correspond to numbers of stitches and are therefore integers.
In the present application, by “knit capable of favoring cellular growth” is meant a knit the knitting pattern of which allows creating voids, pores, channels on the surfaces and/or within the thickness of the knit so that cells may colonize the knit once the knit is implanted in the body of a human being.
Another aspect of the invention is a prosthetic mesh having at least a barbed suture attached thereto, said barbed suture comprising an elongate body made of a yarn of biocompatible material, provided with barbs extending substantially radially out from said elongate body, said barbs being yarns cuts made of a biocompatible material, where said yarns cuts are stitched to said yarn forming said elongate body, said prosthetic mesh being obtained by the method above.
In a first step, step a), of the method of the invention, a knitted structure is produced on a warp knitting machine. The warp knitting machine comprises at least one needle-bed comprising at least three guide bars, a first guide bar B1, a second guide bar B2 and a third guide bar B3. The first guide bar B1 is threaded with first yarns of a biocompatible material, the second guide bar B2 is threaded with second yarns of a biocompatible material, the third guide bar B3 being threaded with third yarns of a biocompatible material. The knitted structure is produced on a determined length along the warp direction corresponding to a total number of N stitches ranging from 1 to N completed along said warp direction by the machine, N being an integer above 7. During this step a), i) a first knit portion is produced along stitches ranging from 1 to x, where 1<x<N, in which the knitting patterns followed by the first, the second and the third guide bars (B1, B2, B3) produce an openworked knit capable of favoring cellular growth, and ii) a second knit portion is produced for stitches ranging from (x+1) to N, in which the knitting pattern followed by said second and third guide bars (B2, B3) produces chain stitches and the knitting pattern followed by the first guide bar B1 produces at least a partial weft in which said first yarns complete weft stitches with at least one of said chain stitches, thereby producing at least one weft stitched chain stitch.
The warp knitting machine may be for example a crochet machine or a raschel knitting machine or a Jacquard machine. Warp knitting machines have a warp yarn for each needle.
By “chain stitch” is meant according to the present application a stitch construction where both over and underlapping are always carried out across the same needle. One chain stitch of a knit therefore involves only one warp yarn, in other words involves only one yarn in the warp direction. The tensile strength of one chain stitch is therefore the tensile strength of said single warp yarn involved in the construction of the chain stitch.
The warp knitting machine may comprise one or more needle-bed(s). For example, the warp knitting machine may comprise two needle-beds. Such double needle-bed machines allow producing bidimensional knits and three-dimensional knits.
In the present application by “bidimensional knit” is meant a knit obtained on a warp knitting machine with the use of one needle-bed only, whatever the number of needle-beds present in the machine, and whatever the number of guide bars present in said one needle-bed. For example, a bidimensional knit may be obtained with two guide bars or more, as long as said guide bars all belong to one needle-bed only. Bidimensional knits may also be obtained on a Jacquard machine, where each guide bar elements are independent.
In the present application by “three-dimensional knit” is meant a knit obtained on a warp knitting machine with the use of two needle-beds, with yarns crossing from a needle-bed to the other.
In embodiments, the warp knitting machine comprises two needle-beds, a first needle-bed comprising said first, second and third guide bars (B1, B2, B3) described above, and a second needle-bed comprising fourth guide bar B4, fifth guide bar B5 and sixth guide bar B6. The fourth guide bar B4 is threaded with fourth yarns of a biocompatible material, the fifth guide bar B5 is threaded with fifth yarns of a biocompatible material, the sixth guide bar B6 is threaded with sixth yarns of a biocompatible material. In such embodiments, the first and second knit portions may be produced by using the six guide bars (B1, B2, B3, B4, B5 and B6).
In such embodiments, step a) may comprise a step 0) occurring before step a)i) as follows:
0) a connecting knit portion is produced along stitches ranging from 1 to y, where 1<y<x<N, in which the knitting patterns followed by first, second, third, fourth, fifth and sixth guide bars (B1, B2, B3, B4, B5, B6) produce a three-dimensional openworked knit capable of favoring cellular growth, said knit having a first face produced on said first needle-bed by said first, second and third yarns from said first, second and third guide bars (B1, B2, B3), and a second face, produced on said second needle-bed by said fourth, fifth and sixth yarns from said fourth, fifth and sixth guide bars (B4, B5, B6), said first and second faces being linked together by some of the second, third, fourth and/or fifth yarns, preferably by some of the third and/or fourth yarns, crossing from the first needle-bed to the second needle-bed and vice-versa, thereby forming linking yarns,
and, in step i), the first knit portion is produced along stitches ranging from (y+1) to x, in which the knitting patterns followed by the first, second and third guide bars (B1, B2, B3) produce on the first needle-bed a first bidimensional openworked knit capable of favoring cellular growth, and in which the knitting patterns followed by the fourth, fifth and sixth guide bars (B4, B5, B6) produce on the second needle-bed a second bidimensional openworked knit capable of favoring cellular growth,
said first and second bidimensional openworked knits being independent from each other,
and, in step ii), the second knit portion is produced for stitches ranging from (x+1) to N, in which:
on said first needle-bed, a first needle-bed second knit portion is produced, in which the knitting pattern followed by said second and third guide bars (B2, B3) produces chain stitches and the knitting pattern followed by the first guide bar B1 produces at least a partial weft in which said first yarns complete weft stitches with at least one of said chain stitches, thereby producing at least one first weft stitched chain stitch,
on said second needle-bed, a second needle-bed second knit portion is produced, in which the knitting pattern followed by said fourth and fifth guide bars (B4, B5) produces chain stitches and the knitting pattern followed by the sixth guide bar B6 produces at least a partial weft in which said sixth yarns complete weft stitches with at least one of said chain stitches, thereby producing at least one second weft stitched chain stitch,
said first needle-bed second knit portion and said second needle-bed second knit portion being independent from each other.
In the present application, “y” corresponds to a number of stitches and is therefore an integer.
In the present application, by “independent knits” with respect to two knits produced, for example simultaneously, on a double-bed knitting machine, is meant one knit produced on the first needle-bed and a second knit produced on the second needle-bed, with no yarns from one needle-bed crossing to the other needle-bed during the production of said two independent knits.
In the present application, the terms “weft stitched chain stitch”, “first weft stitched chain stitch” and “second weft stitched chain stitch” all relate to weft stitched chain stitches obtained according to the method of the invention and generally referred to as “weft stitched chain stitch”, the terms “first weft stitched chain stitch” and “second weft stitched chain stitch” being used for sake of clarity when two needle-beds are used, as it may be useful to distinguish the first weft stitched chain stitches obtained with the first needle-bed from the second weft stitched chain stitches obtained with the second needle-bed.
In embodiments where the warp knitting machine comprises a first needle-bed comprising first, second and third guide bars (B1, B2, B3) and a second needle-bed comprising fourth, fifth and sixth guide bars (B4, B5, B6) as described above, the cutting step bº) may comprise the following steps:
cutting the first needle-bed second knit portion along the warp direction on both sides of said at least one first weft stitched chain stitch and along an edge separating the first needle-bed second knit portion from the first bidimensional openworked knit, so as to remove the first needle-bed second knit portion from the knitted structure while maintaining said first weft stitched chain stitch attached to the first bidimensional openworked knit,
cutting the second needle-bed second knit portion along the warp direction on both sides of said at least one second weft stitched chain stitch and along an edge separating the second needle-bed second knit portion from the second bidimensional openworked knit, so as to remove the second needle-bed second knit portion from the knitted structure while maintaining said second weft stitched chain stitch attached to the second bidimensional openworked knit,
and the method may further comprise the following steps occurring after step bº):
cº) optionally cutting said linking yarns from the three-dimensional openworked knit obtained in step a)0) along stitches ranging from 2 to y,
dº) opening the knitted structure so as to spread in a single plane the part of the knitted structure obtained from the first needle-bed and the part of the knitted structure obtained from the second needle-bed,
wherein the first bidimensional openworked knit, the connecting knit portion, optionally cut according to step cº), and the second bidimensional openworked knit form altogether the mesh; the second or third yarn forming part of said at least one first weft stitched chain stitch forms the elongate body of a first barbed suture attached to the first bidimensional openworked knit, the first yarns cuts extending from said weft stitches of said at least one first weft stitched chain stitch forming said barbs of said first barbed suture; the fourth or fifth yarn forming part of said at least one second weft stitched chain stitch forms the elongate body of a second barbed suture attached to the second bidimensional openworked knit, the sixth yarns cuts extending from said weft stitches of said at least one second weft stitched chain stitch forming said barbs of said second barbed suture.
In the present application, the terms “barbed suture”, “first barbed suture” and “second barbed suture” all relate to barbed sutures obtained according to the method of the invention and generally referred to as “barbed suture”, the terms “first barbed suture” and “second barbed suture” being used for sake of clarity when two needle-beds are used, as it may be useful to distinguish the first barbed sutures obtained with the first needle-bed from the second barbed sutures obtained with the second needle-bed.
As will appear from the description below, the method of the invention allows producing prosthetic meshes having barbed sutures attached thereto in a very simple, easy and rapid process. In particular the method of the invention is a cost effective process as there is no need to use sophisticated cutting machines with blades for performing cuts into the body of a monofilament.
It is known that warp knitting machines are capable of producing knits at high production rates. In addition, the knits produced may also show a very long dimension along the warp direction, which is the direction of manufacturing the knit.
As an example, with current existing warp knitting machines, knits of at least 300 meters long may be produced. For example, if the knitted structure of step a) of the method of the invention has a length L corresponding to the N stitches, a plurality of such knitted structures of length L may be obtained on a length of 300 meters, by simply repeating the knitting patterns of stitches 1 to N as many times as possible on the length of 300 meters. The method of the invention therefore allows manufacturing a plurality of meshes having barbed sutures attached thereto on 300 meters long in a very cost effective way, and in particular in only one knitting step.
The three-dimensional openworked knit obtained during step a)0) of the method of the invention is capable of favoring cellular growth and may be obtained thanks to all knitting patterns known from the art allowing to produce a knit with pores, voids, etc. on a double needle-bed warp machine by using the two needle-beds of the machine. Such knitting patterns are well known.
Examples of knitting three-dimensional knits suitable for the present invention are given in the documents WO99/05990, WO2009/031035 and WO2009/071998.
The bidimensional openworked knits obtained during step a)i) of the method of the invention are capable of favoring cellular growth and may be obtained thanks to all knitting patterns known from the art allowing to produce a knit with pores, voids, etc. using only one needle bed of a warp knitting machine. Such knitting patterns are well known.
Examples of knitting two-dimensional knits suitable for the present invention are given in the document WO2009/071998.
In addition, the barbs created in the barbed suture(s) of the mesh produced according to the method for the invention are ineradicable since they are made of yarns cuts, namely first yarns cuts and/or sixth yarns cuts, that stitch through chain stitches pillar.
In embodiments, the knitting pattern followed by the first guide bar B1 during step a)ii) produces at least a partial weft in which said first yarns complete weft stitches with a plurality of chain stitches, thereby producing a plurality of weft stitched chain stitches, and wherein the cutting of step b) is repeated for each weft stitched chain stitch, thereby producing a plurality of barbed sutures attached to the first knit portion.
In embodiments where the warp knitting machine comprises two needle-beds with three guide bars each as described above, the knitting pattern followed by the first guide bar B1 on the first needle-bed, respectively by the sixth guide bar B6 on the second needle-bed, during step a)ii), may produce at least a partial weft in which said first yarns, respectively said sixth yarns, complete weft stitches with a plurality of chain stitches, thereby producing a plurality of first and second weft stitched chain stitches. In such embodiments, the cutting of step b) may be repeated for each of said first and second weft stitched chain stitches, thereby producing a plurality of first barbed sutures attached to the first bidimensional openworked knit, respectively a plurality of second barbed sutures attached to the second bidimensional openworked knit.
The method of the invention therefore allows manufacturing a mesh having a plurality of barbed sutures of significant length each, the plurality of barbed sutures being attached to the mesh.
In current existing warp knitting machines, a high number of chain stitches may be produced along the width of a knit. As an example, 286 or more chain stitches may be produced on the width of a knit. The method of the invention therefore allows producing a mesh having for example from 2 to 20 barbed sutures attached thereto in one single knitting step
Guide bar B1, respectively guide bar B6, may be fed continuously or intermittently with the first yarns, respectively the sixth yarns, during step a)ii). In embodiments, guide bar B1, respectively guide bar B6, is fed continuously with the first yarns, respectively the sixth yarns, during step a)ii).
The method of the invention further allows producing meshes having barbed suture(s) having different functional portions along their length. In particular, the method of the invention allows producing meshes having barbed suture(s) having active portions, namely portions provided with barbs, and passive portions, namely portions free of any barbs. The passive portions may be obtained by simply stopping the feeding of the first guide bar B1, respectively the sixth guide bar B6, with the first yarns, respectively the sixth yarns, for a certain period of time during the knitting process of step aº)ii) of the method of the invention. Meshes with barbed sutures having alternating active portions and passive portions may therefore be obtained by simply intermittently feeding the first guide bar B1, respectively the sixth guide bar B6, during the knitting process. In embodiments, the first guide bar B1, alternatively the sixth guide bar B6, is fed intermittently with said first yarns, alternatively sixth yarns.
Alternatively, barbed sutures having alternating active portions and passive portions may be obtained by modifying the knitting pattern of guide bar B1, respectively of guide bar B6, so that, for one or several determined time periods during step a)ii) of production of the knitted structure, the first yarns, respectively the sixth yarns, do not complete any weft stitches with said weft stitched chain stitch(es).
The method of the invention further allows varying and selecting the length of the barbs according to an easy process. Indeed, the length of the barbs of the barbed sutures of the meshes obtained with the method of the invention will be dependent first on the distance left between a weft stitched chain stitch and the two adjacent chain stitches on both sides of said weft stitched chain stitch, said distance being a function of the knitting pattern used during step a)ii), and second on the location of the cutting line on said distance at the time of the cutting step b) of the method of the invention. The distance left between a weft stitched chain stitch and the two adjacent chain stitches in the first needle-bed second knit portion will be function of the threading-in of the three guide bars (B1, B2, B3) on the first needle-bed, in particular of the threading-in of the second and third guide bars B2 and B3, and optionally of the first guide bar B1. In the same manner, the distance left between a weft stitched chain stitch and the two adjacent chain stitches in the second needle-bed second knit portion will be function of the threading-in of the three guide bars (B4, B5, B6) on the second needle-bed, in particular of the threading-in of the fourth and fifth guide bars (B4, B5) forming the chain stitches. The greater the distance desired, the more empty needles left between two full needles. On the contrary, the smaller the distance desired between two adjacent weft stitched chain stitches, the less empty needles left between two full needles.
In embodiments where the warp knitting machine comprises only one needle-bed, the knitting pattern followed by the first guide bar B1, the second guide bar B2 and the third guide bar B3 may be as described below for a number N of stitches equal to 70, with x=30. All the knitting patterns are given according to the ISO 11676 standard (publication year 2014):
1º) during step a)i), production of the first knit portion capable of favoring cellular growth according to the following knitting pattern for stitches ranging from 1 to 30:                Bar B1: (5.4/3.2/0.1)×10//        Bar B2: (5.4/3.2/0.1)×10//        Bar B3: (0.1/2.3/5.4)×10//        
2º) during step a)ii), production of the second knit portion according to the following knitting pattern for stitches ranging from 31 to 70:                Bar B1: (0.0/2.3/5.5/3.2)×10//        Bar B2: (2.3/2.3/3.2/3.2)×10//        Bar B3: (2.3/2.3/3.2/3.2)×10//        
wherein, in both steps, B1 is threaded 1 full, 3 empty, B2 is threaded 1 full, 3 empty and B3 is threaded 1 full, 3 empty, along the whole width of the machine.
Such a pattern results in a distance between a weft stitched chain stitch and the two adjacent chain stitches of about 3.5 mm.
In embodiments, where the warp knitting machine comprises a first needle-bed comprising three guide bars B1, B2 and B3 and a second needle-bed comprising three guide bars B4, B5 and B6, the knitting patterns followed by the six guide bars may be as described below for a number N of stitches equal to 70, with x=30, and y=6. All the knitting patterns are given according to the ISO 11676 standard (publication year 2014):
1º) During step a)0): for stitches ranging from 1 to 6, production of a three-dimensional openworked knit capable of favoring cellular growth (connecting knit portion) according to the following knitting pattern:                B1: (5.4.3.3/3.2.1.1/0.1.3.3)×2//        B2: (5.4.3.3/3.2.1.1/0.1.3.3)×2//        B3: 0.1.0.1/2.3.2.3/5.4.2.2/0.1.2.2/2.3.4.4/5.4.2.2//        B4: 0.1.0.1/2.3.2.3/4.4.5.4/2.2.0.1/2.2.2.3/4.4.5.4//        B5: (3.3.5.4/3.3.3.2/1.1.0.1)×2//        B6: (3.3.5.4/3.3.3.2/1.1.0.1)×2//        
2º) During step a)i): for stitches ranging from 7 to 30: production of the first knit portion as follows:
On the first needle-bed, production of a first bidimensional openworked knit capable of favoring cellular growth according to the following knitting pattern:                B1: (5.4.3.3/3.2.1.1/0.1.3.3)×8//        B2: (5.4.3.3/3.2.1.1/0.1.3.3)×8//        B3: (0.1.2.2/2.3.4.4/5.4.2.2)×8//        
On the second needle-bed, production of a second bidimensional openworked knit capable of favoring cellular growth according to the following knitting pattern:                B4: (2.2.0.1/2.2.2.3/4.4.5.4)×8//        B5: (3.3.5.4/3.3.3.2/1.1.0.1)×8//        B6: (3.3.5.4/3.3.3.2/1.1.0.1)×8//        
3º) During step a)ii): for stitches ranging from 31 à 70: production of the second knit portion as follows:
On the first needle-bed, production of first needle-bed second knit portion according to the following knitting pattern:                B1: (0.0.0.0/2.3.4.4/5.5.5.5/3.2.1.1)×10//        B2: (2.3.2.2/2.3.3.3/3.2.3.3/3.2.2.2)×10//        B3: (2.3.2.2/2.3.3.3/3.2.3.3/3.2.2.2)×10//        
On the second needle-bed, production of second needle-bed second knit portion according to the following knitting pattern:                B4: (2.2.2.3/2.2.2.3/3.3.3.2/3.3.3.2)×10//        B5: (2.2.2.3/2.2.2.3/3.3.3.2/3.3.3.2)×10//        B6: (1.1.0.0/0.0.2.3/4.4.5.5/5.5.3.2)×10//        
For example, in all the steps, all the guide bars (B1, B2, B3, B4, B5, B6) may be threaded 1 full, 3 empty along the whole width of the machine.
The method of the invention also allows varying and selecting the amount or number of barbs along the length of the suture in an easy way. In particular, the method of the invention allows selecting a specific frequency of barbs along the length of the suture, in other words a number of barbs per centimeter of suture. Such a frequency will depend on the knitting pattern followed by the first guide bar B1, respectively the sixth guide bar B6, threaded with the first yarns, respectively the sixth yarns. In particular, the more weft stitches completed along the warp direction of the chain stitch, the more weft stitches present on the weft stitched chain stitch in the end, and the higher the frequency of barbs on the resulting barbed suture. In embodiments, the knitting pattern followed by the first guide bar B1, respectively the sixth guide bar B6, produces a partial weft in which said first yarns, respectively said sixth yarns, complete from about 4 to about 15 weft stitches/cm along a length of each said weft stitched chain stitch.
In addition, the method of the invention allows producing meshes having barbed suture(s) attached thereto without affecting the tensile strength of the elongate body of the barbed suture(s). Indeed, contrary to cutting methods of the prior art which create the barbs by performing cuttings in the elongate body of the suture, made of a monofilament for example, the method of the invention leaves the yarn forming the elongate body of the suture integrate. The integrity of the yarn is not affected. As a consequence, the tensile strength of the yarn forming the elongate body of a barbed suture of the mesh obtained by the method of the invention is not affected by the presence of the barbs. Moreover, the method of the invention allows using both monofilaments and multifilaments yarns as the elongate body of the suture, whereas the methods of the prior art involving cutting steps request that the elongate body be a unitary structure, such as a monofilament yarn.
In embodiments, the chain stitch yarns, that will form the elongate body of the barbed suture(s), in particular the second, third, fourth and/or fifth yarns, may be monofilaments or multifilaments. In embodiments, the chain stitch yarns are monofilaments yarns, for example having a diameter ranging from about 0.07 mm to about 0.30 mm. In embodiments, the chain stitch yarns are multifilaments. Existing multifilament yarns may show high tenacity, in other words, high tensile strength. In embodiments, the chain stitch yarns may be multifilament yarns having a tensile strength ranging from about 25 cN/dTex to about 40 cN/dTex, for example a tensile strength of about 35 cN/dTex.
In embodiments, the chain stitch yarns may be multifilament yarns having a thickness ranging from 30 to 500 dTex, for example a thickness of 165 dTex.
In embodiments, the first yarns, that will form the barbs of the barbed suture, in particular of the first barbed suture when two needle-beds are used, may be monofilaments or multifilaments. In embodiments, the first yarns are monofilaments. In embodiments, the sixth yarns, that will form the barbs of the second barbed suture, may be monofilaments or multifilaments. In embodiments, the sixth yarns are monofilaments. Monofilaments allow obtaining barbs with higher mechanical properties. For example, the first yarns and the sixth yarns may be selected from monofilaments having a diameter ranging from about 0.15 mm to about 0.30 mm, for example from about 0.20 mm to about 0.30 mm.
The method of the invention allows producing meshes with barbed suture(s), with barbs having varying surface area in a very easy way. In particular, the size and/or the surface area of the barbs of a barbed suture of the mesh obtained by the method of the invention will be dependent on the size of the diameter of the first yarns, respectively the sixth yarns. In embodiments, the first yarns and/or the sixth yarns are monofilaments showing a diameter ranging from 0.07 mm to 0.30 mm. Such a diameter allows obtaining a good fixation of the barbed suture within the biological tissues.
Barbs of varying size may be desired depending on the contemplated surgical application of the mesh. For joining fat and relatively soft tissues, larger barbs may be desired, whereas smaller barbs may be more suitable for collagen-dense tissues. With the method of the invention, the production of small or alternatively large barbs may be easily obtained by simply selecting monofilament yarns for the first and/or sixth yarns of adequate diameters. For example, for obtaining a barbed suture with large barbs according to the method of the invention, monofilament yarns with a diameter ranging from 0.20 mm to 0.30 mm may be used for the first and/or sixth yarns. In embodiments, the first and/or sixth yarns are monofilament yarns showing a diameter ranging from 0.20 mm to 0.30 mm. Alternatively, for obtaining a barbed suture with small barbs according to the method of the invention, monofilament yarns with a diameter ranging from 0.07 mm to 0.10 mm may be used for the first and/or sixth yarns. In embodiments, the first and/or sixth yarns are monofilament yarns having a diameter ranging from 0.07 mm to 0.10 mm.
In some embodiments, a combination of large and small barbs within the same suture may be desirable, for example when the mesh of the invention is used in tissue repair with differing layer structures. Use of the combination of large and small barbs with the same suture wherein barb sizes are customized for each tissue layer will ensure maximum anchoring properties. In embodiments, the barbed suture(s) of the mesh obtained by the method of the invention may have both large and small barbs. Such barbed suture(s) with a combination of large and small barbs may be obtained by using monofilament yarns of a large diameter, for example ranging from 0.20 mm to 0.25 mm, for the first yarns which are threaded on the first guide bar B1, respectively for the sixth yarns which are threaded on the sixth guide bar B6, and monofilament yarns of a small diameter, for example ranging from 0.07 mm to 0.09 mm, for the second yarns which are threaded on the second guide bar B2, respectively for the fifth yarns which are threaded on the fifth guide bar B5, and monofilament yarns of a large diameter, for example ranging from 0.20 mm to 0.40 mm, for the third yarns which are threaded on the third guide bar B3, respectively for the fourth yarns which are threaded on the fourth guide bar B4.
All the yarns, namely the first, second, third, fourth, fifth and sixth yarns used for forming the knitted structure in the method of the invention are made of a biocompatible material. The biocompatible material may be identical or different from one yarn to another. The biocompatible material may be synthetic or natural. The biocompatible polymer material may be biodegradable, non-biodegradable or a combination of biodegradable and non-biodegradable. The term “biodegradable” as used herein is defined to include both bioabsorbable and bioresorbable materials. By biodegradable, it is meant that the materials decompose, or lose structural integrity under body conditions (e.g., enzymatic degradation or hydrolysis) or are broken down (physically or chemically) under physiologic conditions in the body such that the degradation products are excretable or absorbable by the body.
The biocompatible material may be selected from the group consisting of biodegradable polymers, non-biodegradable polymers, and combinations thereof.
Non-biodegradable materials that may be used as biocompatible material for the yarns of the method of the invention include polyolefins, such as polyethylene, polypropylene, copolymers of polyethylene and polypropylene, and blends of polyethylene and polypropylene; polyamides (such as nylon); polyamines, polyimines, polyesters such as polyethylene terephthalate; polytetrafluoroethylene; polyether-esters such as polybutester; polytetramethylene ether glycol; 1,4-butanediol; polyurethanes; and combinations thereof. In other embodiments, non-degradable materials may include silk, collagen, cotton, linen, carbon fibers, titanium, and the like. The polypropylene may be isotactic polypropylene or a mixture of isotactic and syndiotactic or atactic polypropylene.
Biodegradable materials that may be used as biocompatible material of the yarns of the method of the invention include polylactic acid (PLA), polyglycolic acid (PGA), oxidized cellulose, polycaprolactone (PCL), polydioxanone (PDO), trimethylene carbonate (TMC), polyvinyl alcohol (PVA), polyhydroxyalkanoates (PHAs), copolymers of these materials and mixtures thereof.
In embodiments, the biocompatible material is selected from polyethylene, polypropylene, polyester such as polyethylene terephthalates, polyamide, silicone, polyether ether ketone (PEEK), polyarylether ether ketone (PAEK), polylactic acid (PLA), polycaprolactone (PCL), polydioxanone (PDO), trimethylene carbonate (TMC), polyvinyl alcohol (PVA), polyhydroxyalkanoate (PHA), polyglycolic acid (PGA), copolymers of these materials, and mixtures thereof.
In embodiments, the biocompatible material used for the second and fifth yarns is polyethylene. The polyethylene may be a ultra high molecular weight polyethylene conferring to a multifilament yarn made therefrom a high tensile strength. In embodiments, the second and/or fifth yarns may be polyethylene multifilament yarns having a tensile strength ranging from about 25 cN/dTex to about 40 cN/dTex, for example a tensile strength of about 35 cN/dTex. Such polyethylene multifilament yarns made from ultra high molecular weight polyethylene and provided with such a tensile strength are commercially available from the company DSM under the tradename “Dyneema Purity®”.
In embodiments, the biocompatible material used for the second and fifth yarns is polyethylene terephthalate. In embodiments, the second and fifth yarns may be polyethylene terephthalate multifilament yarns having a tensile strength ranging from about 25 cN/dTex to about 40 cN/dTex, for example a tensile strength of about 35 cN/dTex. In other embodiments, the second and fifth yarns may be high tenacity polyester yarns having a thickness ranging from 30 to 500 dTex, for example of 165 dTex.
In embodiments, the biocompatible material used for the first, third, fourth and/or sixth yarns is polypropylene. In embodiments, the first, third, fourth and/or sixth yarns are polypropylene monofilaments. Polypropylene may confer rigidity to the monofilaments and therefore to the barbs obtained therefrom.
The method of the invention allows customizing the elongate body and the barbs of the barbed suture(s) attached to the mesh in function of the contemplated surgical application. For example, if the barbed suture(s) is/are to be used to fix the mesh in skin or tendon, the barbs may be made relatively short and more rigid, for example by using polypropylene monofilament for the first, third, fourth and/or sixth yarns, to facilitate entry into this rather firm tissue. Alternatively, if the barbed suture(s) is/are intended for use in fatty tissue, which is relatively soft, the barbs may be made longer and spaced further apart to increase the ability of the suture(s) to grip the soft tissue.
In a second step, step b), of the method of the invention, the second knit portion is cut along the warp direction on both sides of said at least one weft stitched chain stitch and along an edge separating the second knit portion from the first knit portion, so as to remove the second knit portion from the knitted structure while maintaining said weft stitched chain stitch attached to the first knit portion.
In embodiments, where the knitting pattern followed by the first guide bar B1 during step a)ii) produces at least a partial weft in which said first yarns complete weft stitches with a plurality of chain stitches, thereby producing a plurality of weft stitched chain stitches, the cutting of step b) is repeated for each weft stitched chain stitch, thereby producing a plurality of barbed sutures attached to the first knit portion.
In embodiments where the warp knitting machine comprises a first needle-bed comprising first, second and third guide bars (B1, B2, B3) and a second needle-bed comprising fourth, fifth and sixth guide bars (B4, B5, B6) as described above, the cutting step bº) may comprise the following steps:
cutting the first needle-bed second knit portion along the warp direction on both sides of said at least one first weft stitched chain stitch and along an edge separating the first needle-bed second knit portion from the first bidimensional openworked knit, so as to remove the first needle-bed second knit portion from the knitted structure while maintaining said at least one first weft stitched chain stitch attached to the first bidimensional openworked knit, the second or third yarn forming part of said at least one first weft stitched chain stitch forming the elongate body of a first barbed suture attached to the first bidimensional openworked knit, the first yarns cuts extending from said weft stitches of said at least one first weft stitched chain stitch forming said barbs of said first barbed suture,
cutting the second needle-bed second knit portion along the warp direction on both sides of said at least one second weft stitched chain stitch and along an edge separating the second needle-bed second knit portion from the second bidimensional openworked knit, so as to remove the second needle-bed second knit portion from the knitted structure while maintaining said at least one second weft stitched chain stitch attached to the second bidimensional openworked knit, the fourth or fifth yarn forming part of said at least one second weft stitched chain stitch forming the elongate body of a second barbed suture attached to the second bidimensional openworked knit, the sixth yarns cuts extending from said weft stitches of said at least one second weft stitched chain stitch forming said barbs of said second barbed suture.
In embodiments, said elongate body(ies) of said second barbed suture(s) is/are formed of fifth yarns only.
In embodiments, where the knitting pattern followed by the first guide bar B1 on the first needle-bed, respectively by the sixth guide bar B6 on the second needle-bed, during step a)ii), produces at least a partial weft in which said first yarns, respectively said sixth yarns, complete weft stitches with a plurality of chain stitches, thereby producing a plurality of first and second weft stitched chain stitches, the cutting of step b) is repeated for each of said first and second weft stitched chain stitches, thereby producing a plurality of first barbed sutures attached to the first bidimensional openworked knit, respectively a plurality of second barbed sutures attached to the second bidimensional openworked knit.
For each of such attached first and second weft stitched chain stitches, the chain stitch yarns, coming either from guide bar B2 (second yarns), B3 (third yarns), B4 (fourth yarns) and/or B5 (fifth yarns), preferably coming from guide bar B2 and/or guide bar B5, will form the elongate body of the thus obtained barbed sutures (first and/or second barbed sutures), and the first or sixth yarns cuts extending from the weft stitches of the first and second weft stitched chain stitches will form the barbs of the thus obtained barbed sutures (first and/or second barbed sutures).
In embodiments, the cutting step may be performed on line, namely while the knitted structure produced at step a) is still on the knitting machine. For example, the knitting machine may be provided with adequate blades. Alternatively, the cutting step may be performed off line, for example with pairs of scissors. For example, the cutting step may be performed by LASER cutting, high frequency welding cutting, roller cutting and/or hot resistance cutting.
In embodiments where the first and/or sixth yarns are monofilaments, the cutting step may be performed via melting the monofilaments at a temperature above their melting point so as to cut said monofilaments. Such a cutting step may be performed on line or off line.
In embodiments where the knitting machine used in the method of the invention comprises two needle-beds and six guide bars are used as described above, after the cutting step b) as described above, the knitted structure is then opened so as to spread in a single plane the part of the knitted structure obtained from the first needle-bed and the part of the knitted structure obtained from the second needle-bed,
wherein the first bidimensional openworked knit, the connecting knit portion, and the second bidimensional openworked knit form altogether the mesh; the second or third yarn forming part of said at least one first weft stitched chain stitch forms the elongate body of a first barbed suture attached to the first bidimensional openworked knit, the first yarns cuts extending from said weft stitches of said at least one first weft stitched chain stitch forming said barbs of said first barbed suture; the fourth or fifth yarn forming part of said at least one second weft stitched chain stitch forms the elongate body of a second barbed suture attached to the second bidimensional openworked knit, the sixth yarns cuts extending from said weft stitches of said at least one second weft stitched chain stitch forming said barbs of said second barbed suture.
In embodiments, for example when “y” is greater than 2, linking yarns from the three-dimensional openworked knit obtained in step a)0) may be cut along stitches ranging from 2 to y, such a step taking place after the cutting step b) described above and before opening the knitted structure in a single plane. The purpose of such a step is to reduce the height of the connecting knit portion in the final configuration of the mesh, when it is spread in a single plane, in order to avoid generating an extra thickness in the middle of the mesh.
After cutting step b) of the method of the invention, the first and/or sixth yarns cuts forming the barbs may generally extend substantially radially out of the chain stitch yarn forming the elongate body of the barbed suture along an angle between the first and/or sixth yarns cuts and the chain stitch yarn of about 90°. In the present application, the angle between the first and/or sixth yarns cuts and the yarn forming the elongate body is measured with a Profile Projector ORAM 300V geometric.
The angle between the first and/or sixth yarns cuts and the yarn forming the elongate body may be modified by submitting the attached barbed suture to a stretching treatment. For example, the angle between the first and/or sixth yarns cuts and the yarn forming the elongate body may be modified so that said angle reaches 45°, 35°, or 33°. The method of the invention therefore allows selecting the adequate angle between the barbs and the elongate body of the barbed suture for an optimized fixation in the biological tissues.
In embodiments, the method further comprises a stretching step during which the second knit portion produced in step a)ii) and/or the attached barbed suture(s) obtained in step bº) is(are) submitted to a stretching treatment. The stretching treatment may comprise a step of stretching the second knit portion or the attached barbed suture(s) in the warp direction. For example, the stretching treatment may be performed by using a traction testing machine such as Hounsfield model H5KS in which a first end of the second knit portion or the first end of an attached barbed suture is grasped by a fixed jaw of the machine and the opposite end of the second knit portion or of the attached barbed suture is grasped by a moving jaw. By moving away from the fixed jaw, the moving jaw stretches the second knit portion or the attached barbed suture.
On an industrial scale, the stretching treatment of the second knit portion in the warp direction may be performed on a heat-setting machine for example. By stretching the second knit portion in the warp direction, all weft stitched chain stitch(es) of the second knit portion are stretched, and as a consequence, all the attached barbed sutures are stretched.
In embodiments, the attached barbed suture(s) is/are stretched from about 0% to about 90%, which means that the stretched attached barbed suture(s) show(s) a length from about 0% to about 90% greater than the initial length of the attached barbed suture.
In embodiments, the second knit portion and/or the attached barbed suture(s) are stretched at 40%, which means that each of the second knit portion and/or the attached barbed suture(s) shows a length 40% greater than their initial length for each. Such a stretching step of 40% may result in the angle between the first and/or sixth yarns cuts and the yarn forming the elongate body be modified to reach about 45°. Such an angle between the first and/or sixth yarns cuts and the yarn forming the elongate body of the barbed suture may be desirable for barbed sutures intended to be used in soft biological tissues.
In other embodiments the second knit portion and/or the attached barbed suture(s) are stretched at 80%, which means that each of the second knit portion and/or the attached barbed suture(s) shows a length 80% greater than their initial length for each. Such a stretching step of 80% may result in the angle between the first and/or sixth yarns cuts and the yarn forming the elongate body be modified to reach about 35°. Such an angle between the first and/or sixth yarns cuts and the yarn forming the elongate body of the barbed suture may be desirable for barbed sutures intended to be used for anchoring purposes in dense biological tissues such as muscles.
In other embodiments the second knit portion and/or the attached barbed suture(s) are stretched at 90%, which means that each of the second knit portion and/or the attached barbed suture(s) shows a length 90% greater than their initial length for each. Such a stretching step of 90% may result in the angle between the first and/or sixth yarns cuts and the yarn forming the elongate body be modified to reach about 33°. Such an angle between the first and/or sixth yarns cuts and the yarn forming the elongate body of the barbed suture may be desirable for barbed sutures intended to be used for anchoring purposes in dense biological tissues such as muscles.
In embodiments, the attached barbed suture(s) may be submitted to a twisting treatment, for example for giving to the barbs a helical pattern. Such a treatment may be performed with a rotor machine.
In embodiments, the method of the invention further comprises a heat-setting step during which either the second knit portion produced in step a)ii) or the attached barbed suture(s) resulting from step b) is(are) submitted to a heat-setting treatment. The heat-setting treatment is intended to fix the barbed suture in the desired configuration. The heat-setting step may take place either between step a) and b), namely before the cutting step, or after step b), namely after the cutting step. For example, in case the second knit portion or the attached barbed suture(s) are submitted to a stretching treatment and/or a twisting treatment, they may simultaneously be submitted to a heat-setting treatment, so that the barbs configuration regarding for example the angle made between the first and/or sixth yarns cuts and the elongate body and/or the helical pattern obtained by the twisting treatment are fixed.
The heat-setting treatment may comprise a step of heating the second knit portion or the attached barbed suture(s) at a temperature ranging from 30° C. to 230° C. during a time period ranging from 1 min to 4 min. The heat-setting treatment may be performed on a heat-setting machine.
The mesh having one or more barbed suture(s) attached thereto obtained by the method of the invention may be sterilized by any means within the purview of those skilled in the art.
The barbed suture(s) of the mesh obtained by the method of the invention may be coated or impregnated with one or more medico-surgically useful substances which accelerate or beneficially modify the healing process when the barbed suture(s) is/are applied to a surgical site. In certain embodiments, the coating may be formed from biodegradable polymers selected from the group consisting of lactones, carbonates, polyorthoesters, hydroxyalkoanates, hydroxybutyrates, bioactive agents, polyanhydrides, silicone, calcium stearoyl lactylates, vinyl polymers, high molecular weight waxes and oils, natural polymers, proteins, polysaccharides, suspendable particulates, dispersible particulates, microspheres, nanospheres, rods, homopolymers thereof, copolymers thereof, and combinations thereof.
Suitable bioactive agents include, for example, biocidal agents, antimicrobial agents, antibiotics, anti-proliferatives, medicants, growth factors, anti-clotting agents, clotting agents, analgesics, anesthetics, anti-inflammatory agents, wound repair agents and the like, chemotherapeutics, biologics, protein therapeutics, monoclonal or polyclonal antibodies, DNA, RNA, peptides, polysaccharides, lectins, lipids, probiotics, diagnostic agents, angiogenics, anti-angiogenic drugs, polymeric drugs, and combinations thereof.
Bioactive agents include substances which are beneficial and tend to promote the healing process. For example, the barbed suture(s) of the mesh obtained by the method of the invention can be provided with a bioactive agent that will be deposited at the sutured site. The bioactive agent can be chosen for its antimicrobial properties, capability for promoting wound repair and/or tissue growth, or for specific indications such as thrombosis.
The barbed suture(s) of the mesh obtained by the method of the invention may additionally comprise a needle at their free end. The needle attachment may be made by any conventional method such as crimping, swaging, and the like.
The prosthetic mesh having one or more barbed suture(s) attached thereto obtained by the method of the invention may be utilized in any open endoscopic or laparoscopic methods. For example, the prosthetic mesh having one or more barbed suture(s) attached thereto obtained by the method of the invention may be utilized for the treatment of hernia.
For example, the mesh obtained by the method of the invention may play its function of abdominal wall repair while the one or more barbed sutures attached thereto may be used by the surgeon in order to fix the mesh to the abdominal wall. The surgeon does not have to look for sutures at the time he needs to fix the mesh to the biological tissue. Moreover, because of the barbed nature of the suture(s) attached to the mesh, the surgeon needs not perform surgical knots. The barbs of the attached barbed suture(s) perform the anchoring function of the suture into the biological tissue very efficiently.